Fans are often incorporated in conventional electronic devices to cool the electronic components included in the electronic devices. A fan incorporated in an electronic device reduces an electronic component's temperature that is generated due to the operation of the electronic device, the surrounding environment, or the like; thus, it is possible to avoid a failure of the electronic device due to heat or to protect a user from burn injuries, or the like, if he or she touches a high-temperature electronic device.
In recent years, the number of electronic components has increased because electronic devices have various functions, and pressure loss has increased in accordance with the reduced size of the electronic devices; therefore, the rotating speed of fans has been increased, which causes the problem of noise due to the operation sound of the fans. For electronic devices that need to be quietly operated, it is preferable that, in the design stage of the electronic devices, consideration is given to an appropriate cooling design, selection of a fan, control of the rotating speed of the fan, and the like.
In one mode for prediction of noise due to a fan in an electronic device, there is a method for predicting noise by using the no-load and rated rotating speeds that are provided by a fan maker, or the like, and by using a sound pressure level that is obtained at a position one meter away from the front face on the air-intake side. In another mode for prediction of noise due to a fan in an electronic device, there is a method for predicting noise on the basis of load noise at an operating point.
Recently, there has been a technology for conducting thermal analysis to predict the pressure difference between the front and back of a fan at an operating point and, by using load noise of the fan, PQ characteristics, or the like, predicting load noise and an air volume at an operating point. Furthermore, recently, there has been a technology for predicting noise that is transmitted to the end of a duct by an air blower. Moreover, in recent years, there has been a technology for drawing a sound ray that indicates the shortest transmission route from a noise source to a sound receiving point behind a wall and calculating distance attenuation, diffraction attenuation, and the like so as to predict noise at the sound receiving point.
Japanese Laid-open Patent Publication No. 2001-108642
Japanese Laid-open Patent Publication No. 08-123434
Japanese Laid-open Patent Publication No. 04-165900
Conventional technologies have a problem in that it is difficult to predict useful sound transmission characteristics inside an electronic device. Specifically, the technology for conducting thermal analysis to predict load noise at an operating point is not used for predicting sound transmission characteristics inside an electronic device. In the technology for predicting noise that is transmitted to the end of a duct, the shape of the duct, attenuation with respect to each arranged electronic component, and the like are measured in advance and manually input by a user. Because the shape of a duct and electronic components arranged in a newly-designed electronic device are different from conventional ones, large errors may occur if values that are measured using existing products are used.
Furthermore, in the technology for drawing a sound ray that is the shortest transmission route from a noise source to a sound receiving point, because distance attenuation and diffraction attenuation are calculated with respect to sound transmission characteristics inside a complicated electronic device, the amount of calculation is increased; therefore, the technology is not suitable for prediction of sound transmission characteristics inside an electronic device. Analysis tools, such as statistical energy analysis (SEA), finite element method (FEM), and boundary element method (BEM), are generally known. For such an analysis tool, a user is preferable to have high-level skills in order to create models, prepare a database in advance, and the like. It is needless to say that, if a user checks a cross-sectional drawing and sets a sound ray inside an electronic device, the amount of work for drawing the sound ray is increased as the number of fans and microphones are large.